Gravity and Magnetic Survey in Southwestern Part of Cuddapah Basin, India and its Implication for Shallow Crustal Architecture and Mineralization

Abstract

Gravity and magnetic surveys were carried out in southwestern part of Cuddapah basin (CB) covering an area of ~3660 km2. Southwestern part of CB gained lot of attention after discovery of second most important uranium province in India. Some non-metallic industrial minerals and base metal occurrence are also reported in the study area. Present study with high spatial resolution gravity-magnetic survey aims to decipher detail basin geometry, nature of sediments, along with possible mineral deposits in SW part of CB. The gravity survey comprising short and long wavelength anomalies brought out sedimentary characteristics and basement architecture underneath the sediments. The long wavelength features of the gravity map shows gneissic basement, which is characterized by both basic and acid magmatic intrusive. Residual gravity anomaly map shows good correspondence with the exposed high density basaltic rock units and also brought out occurrence of concealed high density litho-units, which have significance for mineral prospecting. The magnetic map shows that both sediments and underneath basement are non-magnetic in nature except SW part of the study area, where study suggests occurrence of concealed mafic lensoid body. Euler solutions and combined gravity-magnetic modelling further facilitated for understanding of structural feature and basement geometry. Based on the integrated gravity and magnetic study mineral prospecting zones have been delineated for further detailed study.

Insights into crustal architecture and tectonics across Palghat Cauvery Shear Zone, India from combined analysis of gravity and magnetic data

“…It is to be noted that in the case of RTE, the geomagnetic field is predominantly horizontal. For the induced type of magnetization, the magnetic body near the magnetic equator will oppose the geomagnetic field of the earth and negative (low) anomaly will be recorded (Dobrin & Savit, 1988; Ganguli et al, 2019; Ganguli, Pal, Rama Rao, & Sunder Raj, 2020; Mishra, 2011). Hence in general, an increase in negative anomaly (magnetic low) indicates an increase in susceptibility and positive (magnetic high) anomaly will be observed over diamagnetic and paramagnetic bodies.…”

“…The present study area represents magnetically heterogeneous crust, and magnetic signal contents high‐frequency anomalies and noise, which can perturb the anomaly trend and mask the meaningful geological attributes. The gridded magnetic data was upward continued to an elevation of 100 m to suppress the high‐frequency features, or noise contents (Ganguli et al, 2019, 2020; Hearst & Morris, 2001; Jacobsen, 1987; Kumar et al, 2009) and then RTE filter was applied. This provides the removal of high‐frequency noise of the data without significantly smoothening, in context to the present aim and scale of the study.…”

Insights into the crustal architecture from the analysis of gravity and magnetic data across Salem-Attur Shear Zone (SASZ), Southern Granulite Terrane (SGT), India: an evidence of accretional tectonics

“…6. In general, for the present survey area, the lithounits with ferromagnetic mineral content (high susceptibility) will give a magnetic low, and lithounits with diamagnetic mineral con-tent will provide a magnetic high (Ganguli et al, 2019(Ganguli et al, , 2020a.…”

“…The power spectrum analysis of the gravity and magnetic data has been found very useful for assessing the approximate depth of the causative bodies (Spector and Grant, 1970;Blakely, 1996;Ganguli et al, 2020 a, b;Kumar et al, 2020b;Sahoo and Pal, 2020). The power spectrum of potential field data provides a correlation between finite depth sources of the bodies and finite range of wavelength using the relationship P(w) = A exp(-2|w|h), where P(w) is the power spectrum, A is the constant for randomly distributed source, w is the wave-number; h is the depth to the source (Ganguli et al, 2019).…”

“…In the present study, we have acquired high-density gravity-magnetic data. It leads to high-resolution potential field maps followed by detail analysis of their derivative maps (Vaish and Pal, 2015;Kumar et al, 2019;Ganguli et al, 2019Ganguli et al, , 2020a and joint gravity-magnetic modelling to address the critical issues. The collected rock samples provide information about density and susceptibly values which facilitate for understanding and the correlation of gravity-magnetic signatures.…”